Bjelland D W, Weigel K A, Coburn A D, Wilson R D
Department of Dairy Science, University of Wisconsin, Madison 53706.
Department of Dairy Science, University of Wisconsin, Madison 53706.
J Dairy Sci. 2015 Jul;98(7):4934-44. doi: 10.3168/jds.2014-9014. Epub 2015 May 7.
Recent evidence has suggested that some of the decline in reproductive ability in dairy cattle has been caused by embryonic death. The current study compared expected genomic inbreeding from sire-dam mating pairs to genomic inbreeding from live progeny in an attempt to determine how embryonic inbreeding may affect fertility. A total of 11,484 Holstein cattle with 43,485 SNP markers and pedigree information were available for analysis. A total of 412 sire-dam-progeny trios in which all animals had reliable genotypes were discovered. After removal of trios because of parentage errors, 374 remained for analysis. Additionally, a total of 3,031 animals comprising 3,906 genotyped full-sibling pairs were available for comparison. Expected genomic inbreeding measures were calculated by predicting homozygosity independently per SNP (FPHE) in sire-dam mating pairs and by simulating progeny using phased haplotype information (FROHE and FPHE). Actual genomic inbreeding measures were calculated using the percent homozygosity of all SNP (FPH) and using runs of homozygosity (FROH). Average FPHE values (62.8±0.78%) were slightly lower than FPH (63.1±1.12%), when considering each SNP independently. After phasing haplotypes, FPHE (62.5±0.83%) was again slightly lower than FPH (62.7±1.16%), and FROHE (3.46±1.54%) was slightly lower than FROH (3.53±2.17%). Results suggest increases in expected genomic inbreeding do not explain a large effect on embryo viability at average levels of expected inbreeding. Higher variation in FROH values was present with sire-dam mating pairs exhibiting high FROHE, which may suggest high levels of genomic inbreeding are required for a noticeable effect on overall embryo viability. Genomic inbreeding between full siblings was also compared with moderate correlations (0.47-0.52) present. Overall, expected genomic inbreeding measures were calculated, but results did not suggest a large effect of expected inbreeding on embryo viability.
近期证据表明，奶牛繁殖能力的部分下降是由胚胎死亡所致。当前研究将种公牛与母牛配对的预期基因组近亲繁殖与存活后代的基因组近亲繁殖进行比较，以确定胚胎近亲繁殖如何影响繁殖力。共有11484头荷斯坦奶牛，具备43485个单核苷酸多态性（SNP）标记和系谱信息可供分析。共发现412个种公牛-母牛-后代三联组，其中所有动物都有可靠的基因型。因亲子关系错误剔除三联组后，剩余374个用于分析。此外，共有3031只动物，包括3906个基因分型的全同胞对可供比较。预期基因组近亲繁殖指标通过独立预测每个SNP的纯合性（FPHE）来计算种公牛与母牛配对情况，并使用分阶段单倍型信息模拟后代（FROHE和FPHE）。实际基因组近亲繁殖指标通过计算所有SNP的纯合百分比（FPH）和使用纯合片段（FROH）来计算。单独考虑每个SNP时，平均FPHE值（62.8±0.78%）略低于FPH（63.1±1.12%）。单倍型分阶段后，FPHE（62.5±0.83%）再次略低于FPH（62.7±1.16%），FROHE（3.46±1.54%）略低于FROH（3.53±2.17%）。结果表明，在预期近亲繁殖的平均水平下，预期基因组近亲繁殖的增加并不能解释对胚胎活力有很大影响。FROH值的变异性更高，种公牛与母牛配对表现出高FROHE，这可能表明需要高水平的基因组近亲繁殖才会对整体胚胎活力产生显著影响。全同胞之间的基因组近亲繁殖也进行了比较，相关性适中（0.47 - 0.52）。总体而言，计算了预期基因组近亲繁殖指标，但结果并未表明预期近亲繁殖对胚胎活力有很大影响。
